20556555509 has 12 divisors (see below), whose sum is σ = 24952413024. Its totient is φ = 16853820984.

The previous prime is 20556555433. The next prime is 20556555511. The reversal of 20556555509 is 90555565502.

It is not a de Polignac number, because 20556555509 - 2¹² = 20556551413 is a prime.

It is a Smith number, since the sum of its digits (47) coincides with the sum of the digits of its prime factors.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20556555599) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9118907 + ... + 9121160.

It is an arithmetic number, because the mean of its divisors is an integer number (2079367752).

Almost surely, 2^20556555509 is an apocalyptic number.

It is an amenable number.

20556555509 is a deficient number, since it is larger than the sum of its proper divisors (4395857515).

20556555509 is a wasteful number, since it uses less digits than its factorization.

20556555509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18240104 (or 18240097 counting only the distinct ones).

The product of its (nonzero) digits is 1687500, while the sum is 47.

The spelling of 20556555509 in words is "twenty billion, five hundred fifty-six million, five hundred fifty-five thousand, five hundred nine".